Forms of DNA

See Also: DNA and Z-DNA

A comparative representation of the three forms of DNA
Sources

Synchronize the three applets showing A-, B- and Z-DNA by clicking the checkbox  A              sync jmolAppletB,jmolAppletZ   sync OFF Synchronize 

Helical Parameters of the three forms of DNA
DNA is a very flexible molecule and has the ability to exist in various forms based on the environmental conditions. Naturally occurring DNA double helices are classified into A, B and Z-types. A and B-forms of DNA are the right handed forms whereas Z-DNA is the left handed form. When hydrated the DNA generally assumes B-form. The A conformation is found when there is little water to interact with the helix and is also the conformation adopted by the RNA. The formation of Z-DNA occurs with the methylation of deoxycytosine residues and also during transcription where negative supercoiling stabilizes it.

Structural Transformation between A and B DNA
 AtoB 660    white morph_a-b.pdb animation ON; animation mode PALINDROME; cartoon ON; save state ab 

 AtoB moveto 1.0 0 0 1 0 100.0 0.0 0.0;load/wiki/images/9/9e/Morph_a-b.pdb;animation ON; animation mode PALINDROME; cartoon ON;save state ab Click here and activate the below options 

 AtoB moveto 1.0 0 0 1 0 180.0 0.0 0.0;restore state ab; animation ON;animation mode palindrome;cartoon ON;spacefill on; spacefill 90;wireframe on;wireframe 50;zoom 180;select 9:a,4:b;hbonds ON;hbonds calculate;hbonds 0.09;select!selected; color translucent 0.9;set echo bottom centre;font echo 20 serif bolditalic;color echo green; echo"Base pair shift between A and B DNA" Shift in Base Pair between A-B DNA moveto 1.0 0 0 1 0 400.0 0.0 0.0; restore state ab;cartoon OFF;spacefill ON; spacefill 90; wireframe ON; wireframe 50;select 9:a; select!selected; color translucent 0.9; select!selected; centre selected;zoom 400;set echo bottom centre;font echo 20 serif bolditalic;color echo green; echo"Change in Sugar Puckering from C2' endo in B-DNA to C3' endo in A-DNA" Change in Sugar Puckering from C2' endo in B-DNA to C3' endo in A-DNA moveto 1.0 0 0 1 0 150.0 0.0 0.0;restore state ab;spacefill ON; spacefill 400; zoom 150; cartoon OFF;animation ON; animation mode PALINDROME;set echo bottom centre;font echo 20 serif bolditalic;color echo green; echo"Transition between A-B DNA spacefilling models" Transition between A-B DNA spacefilling models 

 AtoB moveto 1.0 0 0 1 0 100.0 0.0 0.0;load/wiki/images/9/9e/Morph_a-b.pdb;animation ON; animation mode PALINDROME; cartoon ON;save state ab Restore Original State 

Morph Sources